Conventionally, a wireless base station device using a wireless communications system of a CDMA scheme performs controls thereof as described below. In wireless base station devices of a same wireless access scheme, based on conditions such as channel capacities and transmission power levels of the respective base station devices, various kinds of area configurations are considered to be applied to a service area covered by each base station device. To be more specific, in case where a wireless base station device is installed, it is required that, by surveying specific environmental conditions of an installation place, an area configuration be set based on an arrangement design of the base station device in order to avoid interferences with other base station devices.
Specifically, the area configuration is set by, e.g., setting a carrier frequency to be used in a base station device to be installed, setting a maximum transmission power, and selecting a scramble code used for a spread modulation performed when transmitting a downlink signal assigned per each sector of the base station device. Conventionally, these parameters to be set or selected are included in base station information set per each base station device to be installed (or set per each sector thereof, if the base station device to be installed is configured with a plurality of sectors), and, at the time of area configuration, a list of the parameters suitable for the environment of the installation place is prepared to be allocated to each base station device.
In a base station device, wireless resources and a device configuration that correspond to a wireless area configuration are established to commence the operation, based on parameters (hereinafter, referred to as “base station data”) stored in advance in the base station device depending on its installation place, and other parameters set by a radio network controller (RNC), that is an upper-level device of the base station device, at the time of cell setup of the base station device.
In communications between a mobile station and a base station of a wireless communications system, if, for example, a transmission is requested from the mobile station, control information is sent and received via a common channel. Thus, parameters required for an individual channel setup are shared, and, if wireless resources and channel resources of the base station device that are required for individual channel setup are acquired, the individual channel setup is carried out to thereby commence communications for user data. For this purpose, when the operation of the base station device is started, a common channel is first set up, and then a transmission power, whose level is high enough to enable communications with a wireless portable terminal device, is applied by considering an area covered by the base station device.
A baseband unit of the wireless base station device has resources for a channel used for providing a mobile station located within a cell with information on service area (cell) set with respect to the base station device as well as a common channel used for receiving a new call and transmitting control information for setting up the base station device, and other resources for an individual channel for transmitting data and control information on a one-to-one basis between the mobile station and the base station.
FIG. 4 is a block diagram showing an example of configuration of a conventional wireless base station device. The wireless base station device includes a wired transmission line interface (IF) unit 11 connected to an upper-level device (RNC); a frame protocol (FP) processor 12 for performing a frame protocol processing required for interfacing with the wired transmission line; a call controller 13 for performing a call control; a wireless unit 14 for communicating with a mobile station; a reception memory 15 for storing sampling data of uplink reception data outputted from the wireless unit 14; a baseband receiver 20 of an individual uplink channel for performing a baseband reception of the individual uplink channel based on the data stored in the reception memory 15; a baseband receiver 30 of a common uplink channel for performing a baseband reception of the common uplink channel based on the data stored in the reception memory 15; a baseband transmitter 40 of an individual downlink channel for performing an encoding and modulation on individual downlink channel data processed by the frame protocol processor 12; a baseband transmitter 50 of a common downlink channel for performing an encoding and modulation on common downlink channel data processed by the frame protocol processor 12; and a spread processor 16 for, by using a specific spreading code, spread-modulating downlink data outputted from the baseband transmitter 40 of the individual downlink channel and the baseband transmitter 50 of the common downlink channel, and then outputting the spread-modulated downlink data to the wireless unit 14.
Further, the baseband receiver 20 of the individual uplink channel includes a control channel inverse spread unit 21; a data channel inverse spread unit 22; a demodulator 23; a demodulation data memory 24; and a decoder 25.
The baseband receiver 30 of the common uplink channel includes a control channel inverse spread unit 31; a data channel inverse spread unit 32; a demodulator 33; a demodulation data memory 34; and a decoder 35.
The baseband transmitter 40 of the individual downlink channel includes an encoder 41 and a modulator 42.
The baseband transmitter 50 of the common downlink channel includes an encoder 51 and a modulator 52.
The wireless base station device configured as above is connected to an upper-level device (RNC) via the wired transmission line interface unit 11. At a start-up of the base station, firstly, the call controller 13 sets up necessary parameters of the wired transmission line from the base station data, and inputs cell setup data set by the upper-level device to the wireless unit 14 and the baseband signal processor. The parameters to be inputted to the wireless unit 14 include, e.g., a frequency number of a carrier in use. In the baseband signal processor, a parameter of a pilot channel (CPICH), which serves as a reference of the transmission power and a timing of the common downlink channel, is set up. In addition, a scramble code for spread-modulating downlink data outputted from the base station device is set up.
Hereinafter, an initial parameter setting method in a conventional wireless base station device communicating with a plurality of mobile stations (terminal devices) will be described. Recently, to cope with an increase in users of terminal devices, a method (also known as “micro cell method”) of reducing a cell size per each base station device 61 has been employed as shown in the example of area configuration of FIG. 5. In FIG. 5, reference numeral 61 denotes a plurality of wireless base station devices, each of which has a micro cell area 62, surrounded by a plurality of wireless base station devices 63, each of which has a micro cell area 64.
As set forth above, in recent years, the micro cell method has been employed to cope with the increase in users of terminal devices, and cells are becoming smaller. In this case, cells tend to be easily affected by, e.g., landforms, structures such as buildings, or external interferences with neighboring cells. Especially in case of the CDMA scheme, the amount of interference power, that includes an internal interference 65 with the terminal device existing within the cell and an external interference 66 with neighboring cells, is highly dependent upon a channel capacity of the base station device. Considering this, when an area configuration is to be set by a small-scale wireless base station device, it is important to configure a base station and set parameters to be suitable for a surrounding environment of the base station.
Further, as a prior art related to the present invention, there is provided a technique for setting a communications configuration for a wireless base station (see, for example, Patent Document 1). A wireless base station device setting system disclosed therein includes a wireless base station device setting device for setting a communications configuration of a wireless base station device. When the wireless base station setting device receives a setting request notification message from the wireless base station device, the wireless base station setting device deletes information about the wireless base station device among information stored in its information storage unit, and estimates a position of the wireless base station device. Then, the wireless base station setting device reads out, from the information storage unit, a communications configuration of another wireless base station device installed in a vicinity of the estimated position, and determines a communications configuration of the wireless base station device according to the read-out communications configuration of said another wireless base station device as well as the estimated position.
In addition, as another prior art related to the present invention, there is provided a W-CDMA portable phone system having a plurality of wireless base stations and a base station controller for controlling the plurality of wireless base stations (see, for example, Patent Document 2). As disclosed therein, a wireless base station receives a radio signal from another wireless base station, and processes the received radio signal, thereby specifying a control channel of said another wireless base stations. Thereafter, the wireless base station identifies, based on the control channel, a downlink scramble code of the radio signal sent from said another wireless base station. Then, the base station controller determines, based on the identification result from the wireless base station, a downlink scramble code of the wireless base station that has sent the identification result.
In accordance with the initial parameter setting method of the conventional base station device as shown in FIG. 4, if parameters suitable for an installation place and an environment thereof are determined in advance, stored parameters, together with other parameters set by the upper-level device (RNC), are set in the wireless unit 14, the wired transmission line interface unit 11 and the baseband signal processor (not shown) to thereby start the operation.
However, if a place at which the base station device is to be installed is not specified in advance, when the operation is started by installing the base station so that a degree of freedom is given with regard to the installation place, it is difficult to prepare suitable parameters in advance. Especially in a case where a relatively small number of terminal devices are acceptable to the base station device and the base station device is small in size, if predetermined initial parameters are applied without considering the environment depending on the place to be used, there are many cases where proper operations are not possible due to the effects of, e.g., interferences in communications between the base station device and terminal devices and those between neighboring base station devices and terminal devices.
First, let us consider a scramble code to be used for a spread modulation of a downlink signal of a base station device. A terminal device first checks a scramble code number assigned to each cell, measures a reception level of a common channel to thereby select a most suitable base station device among base station devices to which the terminal device has access. However, if, for example, a scramble code number of the base station device to be installed is same as that of a neighboring base station device, an identification of cell is not possible.
In addition, a fixed transmission power is used for a pilot channel (CPICH) and a broadcast control channel from the base station device. In this case, if a set power level is not suitable for an area covered by the base station device, interferences take place to affect terminal devices that are communicating with neighboring base station devices to thereby deteriorate a communications quality.
Further, although a single frequency can be commonly used by adjacent cells in a CDMA scheme, influences of external interference can be reduced by using different frequencies for the area configuration. However, if a different frequency is arbitrarily assigned, and a target base station device to which a handover is expected cannot accept the different frequency that has been arbitrarily assigned, a forced release is carried out to thereby increase a call loss probability. Moreover, since a hard handover is used for transferring a call between cells using different frequencies, a diversity effect, that can be obtained in case of transferring a call between cells using a same frequency by a soft handover, cannot be obtained. Herein, the diversity effect refers to that channels of a current cell and another cell can be used at the same time.
Furthermore, in Patent Document 1, the wireless base station setting device estimates a position of a wireless base station device when it receives a setting request notification message from the wireless base station device, and reads out, from an information storage unit therein, a communications configuration of an existing wireless base station device placed at the vicinity of the estimated position. Then, the wireless base station setting device determines a communications configuration of the wireless base station device based on the readout communications configuration of the existing wireless base station device and the estimated position. Thus, since the wireless base station setting device disclosed in Patent Document 1 does not search neighboring base station devices for itself, it is not possible to obtain information of an actual environment in which the wireless base station device is installed.
Additionally, the wireless base station device, when it accesses to the wireless base station controller to receive information of neighboring base station therefrom, receives a downlink signal of another base station devices by using the information of the neighboring base station to thereby measure a signal level to be used for a position detection. However, since the wireless base station device is configured such that the area configuration is set by a user, it is difficult to perform an optimal area configuration in which communications overheads or interferences with other base station devices are taken into consideration.
Moreover, in Patent Document 2, the wireless base station identifies a downlink scramble code of a radio signal from other wireless base station to thereby determine a downlink scramble code of the wireless base station itself by the base station controller, but fails to consider base station information other than scramble code.
Further, in wireless communications systems, signals are communicated between a base station device (radio base station device) and a plurality of terminal devices by wireless.
Generally, in case of installing and starting up a base station device, setting data (for example, frequency and/or code data) for starting up the base station device is inputted thereto by a worker or engineer who is particularly allowable by a communication provider.
It is however expected that a system in which numerous base station devices each having a small communication area are installed will be used in the future. In this case, it is also supposed that many workers are required, which need immense installation expense. In addition, since the communication area of each base station device is small, it would be quite difficult to install a plurality of base station devices in order to prevent any leakage in such communication area.
For the reason, if a user of a base station device installs it in a desired range for its use by oneself, it is expected that the base station device could be very efficiently installed. However, it is problematic that the communication provider does not usually teach setting data of the base station device to common users.
(Patent Document 1) Japanese Patent Laid-Open Application No. 2005-328152
(Patent Document 2) Japanese Patent Laid-Open Application No. 2005-219478
(Patent Document 3) Japanese Patent Laid-Open Application No. H6-261362